1. Field of the Invention
The present invention relates to a display device using a display panel, a structure of the display panel, and a method of driving the display panel.
2. Description of Related Art
In recent years, plasma display devices using a surface discharge type AC plasma display panel are drawing attention as a large-size and thin-shape color display panel.
FIGS. 1–3 are diagrams showing portions of the structure of a conventional surface discharge type AC plasma display panel.
The plasma display panel (PDP) has a structure for producing a discharge in each pixel between a front glass substrate 1 and a back glass substrate 4 arranged in parallel with each other. The surface of the front glass substrate 4 serves as a display surface. On the back side of the front glass substrate 1, a plurality of longitudinal row electrode pairs (X′, Y′), a dielectric layer 2 covering the row electrode pairs (X′, Y′), and a protection layer 3 made of MgO and covering the back side of the dielectric layer 2 are provided in order. Each row electrode X′, Y′ comprises a transparent electrode Xa′, Ya′ formed of a wide transparent conductive film such as ITO; and a bus electrode Xb′, Yb′ formed of a narrow metal film for compensating the transparent electrode for the conductivity. The row electrodes X′, Y′ are arranged alternately in the vertical direction of the display screen so as to be opposed to each other across a discharge gap g′. Each row electrode pair (X′, Y′) comprises one display line (row) L of a matrix display. The back glass substrate 4 is provided with a plurality of column electrodes D′ arranged in a direction perpendicular to the row electrode pairs X′, Y′; a strip-shaped partitions 5 formed respectively in parallel with one another between the column electrodes D′; and a fluorescent layer 6 formed of read (R), green (G), and blue (B) fluorescent materials for covering the side surfaces of the partitions 5 and the column electrodes D′. Between the protection layer 3 and fluorescent layer 6, a discharge space S′ is formed and filled with an Ne—Xe gas containing, for example, 5 vol % of Xenon. Each display line L includes discharge cells C′ as unit light emission regions at intersections of the column electrodes D′ and row electrodes pairs (X′, Y′), defined by the partitions 5 in the discharge space S′.
To form images on the surface discharge type AC PDP, a so-called subfield method is employed as a method of displaying a halftone image, wherein one field display period is divided into N subfields, in each of which light is emitted a specified number of times corresponding to a weighting of each bit digit of N-bit display data.
In the subfield method, each subfield divided from one field display period consists of a simultaneous reset period Rc, an address period Wc, and a sustain period Ic, as shown in FIG. 4. In the simultaneous reset period Rc, reset pulses RPx, RPy are simultaneously applied between the row electrodes X1′–Xn′ and Y1′–Yn′ which form pairs to simultaneously produce a reset discharge in all discharge cells, thereby once forming a predetermined amount of wall charge in each discharge cell. In the next address period Wc, the row electrodes Y1′–Yn′ of the row electrode pairs are sequentially applied with a scanning pulse SP, while the column electrodes D1′–Dm′ are applied with display data pulses DP1–DPn corresponding to display data for each display line of an image to produce an address discharge (selective erasure discharge). In this event, the discharge cells are divided into a light emission cell in which no erasure discharge is produced so that the wall charge remains formed therein, and a non-light emission cell in which the erasure discharge is produced to extinguish the wall charge, corresponding to image data of the image. In the next sustain period Ic, sustain pulses IPx, IPy are applied to the row electrodes X1′–Xn′ and Y1′–Yn′ which form pairs, a specified number of times corresponding to a weighting of each subfield. In this manner, only light emission cells in which the wall charges remain repeat sustain discharges a number of times corresponding to the number of applied sustain pulses IPx, IPy. This sustain discharge causes Xenon Xe filled in the discharge space S′ to radiate vacuum ultraviolet rays at wavelength of 147 nm. The vacuum ultraviolet rays excite the red (R), green (G), and blue (B) fluorescent layers formed on the back substrate to generate visible light to produce an image corresponding to an input video signal.
In the formation of an image on the PDP, a reset discharge is produced before the start of the address discharge and sustain discharge for stabilizing these discharges, as described above. The address discharge is also produced in each subfield. In the conventional PDP, the reset discharge and address discharge are produced by the sustain discharge in the discharge cells C′ for generating visible light for image formation.
Therefore, light emitted by the reset discharge and address discharge appear on the display surface of the panel to make the screen bright even when a dark image such as a black image is displayed, resulting in a degradation in dark contrast in some cases.